This invention relates to a hydrated granular carrier for a biological treatment apparatus and a method for producing the same and, more particularly, to a living microbe immobilizing carrier used for a biological treatment apparatus for treating waste water and exhaust gas produced in both a living system and an industrial system and a method for producing the same.
A living microbe immobilizing carrier for a biological treatment apparatus which is currently put into practice is a granular carrier comprising completely saponified granular polyvinyl alcohol (PVA) particles and finely ground organic powder, such as finely ground activated charcoal powder coated on the granular particles, and is adapted to utilize adsorption characteristics of the finely ground organic powder coated on the granular particles. Such a conventional carrier is typically disclosed in each of Japanese Patent Publication No. 60318/1989 and Japanese Patent Publication No. 21317/1990. Immobilization of living microbes is carried out by immersing the carrier particles in an aqueous solution in which the living microbes are cultured. The carrier is used in the form of a packed bed or a fluidized bed in the biological treatment apparatus. When the carrier is used in the form of a packed bed, it is required to reduce volume change to a weight of the carrier which has water adsorbed thereto in a treatment apparatus; whereas when it is used in the form of a fluidized bed, it is required that the granular particles exhibit increased strength and the finely ground organic powder is coated on the granular particles with increased strength.
In order to efficiently immobilize the living microbes on a surface of the carrier, it is essential that the finely ground organic powder on a surface of the granular particles exhibits satisfactory adsorption properties and the granular particles exhibit satisfactory water absorption properties. Water absorption properties of the carrier depend on water retention of the polymer of which the granular particles for the carrier are formed and an internal structure of the granular particles. Also, durability of the carrier depends on the internal structure of the granular particles and coat strength of the finely ground organic powder on the granular particles. Nevertheless, the conventional carrier was not fully considered on a function of immobilizing living microbes thereon, durability of the carrier and the like.